中文摘要：

双井子杂岩产出在内蒙古东部林西县西拉木伦河的南北两侧，由片岩、片麻岩和片麻状花岗岩组成。前人对其形成时代认识不一，一种观点认为属于前寒武纪变质岩，另外一种观点认为属于早中生代构造强烈变形产物。本文通过对双井子杂岩开展较为系统的LA-MC-ICP-MS锆石年代学研究，来限定这套杂岩的形成年代。锆石测年结果表明，绿泥石片岩的锆石206Pb/238U年龄值变化于146.3~1970 Ma，年龄比较分散，没有获得一个比较可靠的加权平均年龄。黑云斜长片麻岩的锆石206Pb/238U年龄值变化于146.3~1736 Ma，获得2组比较可靠的年龄：一组由10个点组成，加权平均年龄值为（290.5±2.1）Ma，MSWD=0.36，为早二叠世；另一组由5个点组成，加权平均年龄值为（247.5±3.4）Ma，MSWD=0.12，为早三叠世，可能分别代表原岩中两期岩浆的侵位时间。侵位于杂岩中的花岗伟晶岩的锆石206Pb/238U年龄值变化于206.9~2122 Ma，年龄比较分散，也没有获得一个比较可靠的加权平均年龄。片麻状花岗岩的锆石加权平均年龄值为（278.4±1.4）Ma，MSWD=1.9，可以代表原岩岩体的侵位年龄，为早二叠世。岩石地球化学分析结果表明，双井子杂岩岩石（包括绿泥石片岩、黑云斜长片麻岩和片麻状黑云母花岗岩）成分复杂，其主量元素含量变化较大，SiO2含量变化于61.97%～77.18%，但是所有的岩石样品均具有轻稀土分异明显、富集大离子亲石元素（LILE）的特征，都是U、Nb、Sr、P、Ti相对亏损，而Th、K、Ce、Nd、Hf、Sm、Y和Yb相对富集。与杂岩中的岩石相比，花岗伟晶岩显示明显不同的Ba亏损和Ta富集，而其他元素的富集和亏损趋势则与其几乎一致。因此，总的来说，双井子杂岩是由不同成分和时代的岩石（包括地层和岩浆岩）混合组成。根据前人研究成果和上述锆石年龄数据，推测双井子杂岩的形?

英文摘要：

The Shuangjingzi complex occurs on the southern and northern sides of the Xar Moron River in Linxi County, eastern Inner Mongolia and is composed of schist, gneiss and gneissic granite. There exists controversy over timing of the Shuangjingzi complex. Some researchers hold that it belongs to Precambrian metamorphic rocks,while others argue that it belongs to the Early Mesozoic strong structural deformation products. In this paper, the authors studied zircon geochronology of the main rocks in the Shuangjingzi complex by using the LA-MC-ICP-MS method with the purpose of constraining the timing of the complex. The zircon dating results show that the 206Pb/238U ages of the chlorite schist range from 146.3 Ma to 1970 Ma, with no reliable weighted mean ages obtained due to the too scattered ages. The 206Pb/238U ages of the biotite plagioclase gneiss vary from 146.3 Ma to 1736 Ma, with two reliable weighted mean 206Pb/238U ages of （290.5 ± 2.1） Ma （MSWD = 0.36, n=10） and （247.5 ± 3.4） Ma （MSWD=2.9, n=5）, respectively, indicating that two epochs of magmatic emplacement events took place in the original rocks of the complex during Early Permian and Early Triassic, respectively. The zircons from the granite pegmatite that intruded into the complex do not give a reliable weighted mean age, with the scattered 206Pb/238U ages ranging from 206.9 Ma to 2122 Ma, while the zircons from the gneissic granite occurring within the complex yielded a weighted mean 206Pb/238U age of（278.4±1.4）Ma （MSWD=1.9,n=16）, suggesting that the emplacement of the original rock occurred during Early Permian. Geochemical analyses show that the Shuangjingzi complex, including chlorite schist, biotite plagioclase gneiss and gneissic biotite granite, is characterized by complicated constituents, with SiO2 content from 61.97%to 77.18%. All samples collected from the complex have the features of LREE differentiation, and are enriched in LILE elements with relative depletion of U, Nb, Sr, P and Ti, and enriched in Th, K, Ce, Nd, H